In order to measure forces and torques on a rotating body force measuring devices are usually used which are mounted on the rotating body. To determine the directions of force for each relevant direction of force an appropriate solution is to use at least one accordingly oriented force measuring device, the individual force measuring devices preferably being arranged at a 90° angle to each other. To determine the direction and size of the forces, the force values measured by the individual force measuring devices can be grouped component by component into a force vector.
In order to be able to measure the forces of a propeller of a wind tunnel model, a rotating force measuring device in the form of a propeller force balance (also known as “rotating shaft balance”, RSB) is normally used. This is mechanically attached to the hub of the propeller. Measured forces are transmitted telemetrically via a pairing having a rotating and a fixed coil or, alternatively, via one or more slip rings of a fixed device, for example an evaluation unit or a measured value recorder.
A method for measuring propeller forces of wind tunnel models is known where the occurring propeller forces are measured in all relevant spatial directions once only for each rotation of the propeller in order to calculate the resulting force vector. According to the Nyquist-Shannon theorem, however, the signal components that have frequencies higher than one-half of the rotational frequency of the propeller are not detected. Also, interferences with higher frequencies are not detected and cannot be separated from the actual signal. Since, when rotating force sensors rotate in relation to a spatially fixed force, only position-dependent force components are detected which, for instance, display a sinusoidal progression over one rotation, a precise measurement of the actually occurring force requires a sufficient sampling rate.
Another method is known where the occurring forces are measured with a constant, sufficiently high sampling rate for each rotation. They are then grouped together in force vectors through the numerical determination of their position based on the rotational progress above the adjusted speed. The disadvantage of this method, however, is the direct dependence of the determined force direction and force value on the rotation speed, which means that, for the position to be determined correctly, a constant rotation speed must be assumed.
In view of the foregoing, at least one object is to provide a system and method for measuring forces and torques occurring on a rotating body which does not have the disadvantages mentioned above. In particular, at least one object is to provide such a system and method allowing the forces and torques on a rotating body to be determined precisely and as flexibly as possible and therefore independently of the prevailing rotation speed of the rotating body. In addition, other objects, desirable features, and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.